US3582694A - Electrogasdynamic systems and methods - Google Patents

Abstract

Electrogasdynamic systems in which a plurality of slender gas flow channels carry electrical charges to a downstream charge collector. Each flow channel is of elongate cross section, and the elongate dimension thereof may progressively increase from one end of the channel to the other. Electrical charges are injected into the flow by a corona discharge established in the flow between attractor and corona discharge electrodes extending laterally across the flow in the direction of elongation of the channel cross section and located preferably at the channel side. Adjacent channels are defined by spaced dielectric plates or by spaced rows of conductive wires mutually spaced in the direction of flow and connected externally to an electrical biasing or current-carrying circuit.

Description

6 1 l) *1 3 S R FIP'SSQZ GR 31 582169 1 I i mted States Patent 1 13582 594 [72] Inventor Meredith C. Gourdlne 2,085,735 7/1937 Brion et al. 55/137 5 West 0rangc,N..l. 3,054,553 9/1962 White 230/69 1211 Appl. No. 835,209 3,212,878 10/1965 Bouteille 75/9 [22] Filed June 20,1969 3,400,513 9/1968 Boll 55/103 [45] Patented JIIDC l, 197] 1 g fi rggg fi lmrwnwd 204,361 9/1923 Great Britain 55/138 conuuuamnhmm of lppuuuon Sen N0. 629,665 10/1961 Canada 55/138 601,270 Nov. 15, 1966 now abandoned 848,687 9/1960 Great Britain 310/10 Which in turn is a continuation-in-part of Primary Examiner-D. X. Sliney application Ser. No. 512,083, now Attorney-Brumbaugh, Graves, Donohue 8L Raymond l abandoned.

[54] ELECTROGASDYNAMIC SYSTEMS AND ABSTRACT: Electrogasdynamic systems in which a plurality i METHODS of slender gas flow channels carry electrical charges to a 63 Chins, "Dnwhg as. downstream charge collector. Each flow channel is of elongate cross section, and the elongate dimension thereof may U.S. rogre sively increase from one end of the channel to the 55/122 55/138 other Electrical charges are injected into the flow by a corona ll. discharge in the flow between attractor and of orona di harge electrodes extending laterally across the T 55/133 101v l3, 128-33; 317/103 flow in the direction of elongation of the channel cross section and located preferably at the channel side. Adjacent channels [56] References cued are defined by spaced dielectric plates or by spaced rows of UNITED STATES PATENTS conductive wires mutually spaced in the direction of flow and 2,004,352 6/1935 Simon 310/6 connected externally to an electrical biasing or current-carry- 2,008,246 7/1935 Deutsch 55/123X ing circuit.

PATENTEDJUN 112m 3582.694

SHEET 3 OF 6 HIGH IMPEDANCE LOAD OR vomes SOURCE 50 5/ 20b Me /2 1\\ 5x113: n n 1;, 186 I82 4 58a 56b 58c 56 Z LOW IMPEDANCE 62 LOAD 56a 65 58b 69 56c 65 {3 69 INVENTOR.

MEREDITH C. GOURDINE his ATTORNEYS PATENTED JUN 1 I97! SHEET BF 6 Jwwww mmnmmumm 4%ZI, wk .04

his ATTORNEYS PATENIEU JUN 1 I97! SHEET 5 OF 6 D. c. r145 OURCE FIG.7

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IN VEN 'l'()l MEREDITH C. GOURDINE his 47 7 0 NEYS ELECTROGASDYNAMIC SYSTEMS AND METHODS CROSS-REFERENCES TO RELATED APPLICATIONS This a continuation-in-part of my copending application Ser. No. 60l,270 for Electrogasdynamic Systems and Methods," filed Nov. l5, i966, which, in turn, is a continuation-in-part of application Ser. No. 5l2,083 for Electrogasdynamic Systems, filed Dec. 7, I965, both now abancloned.

BACKGROU N D OF THE INVENTION This invention relates to improved electrogasdynamic methods, systems and apparatus operating on a stream or streams of fluid to effect a conversion between electrical energy and the energies of the stream, or to effect precipitation of particulate matter entrained in the fluid stream.

In using electrogasdynamic prinicples to derive electrical energy from the kinetic, the converter and thermal energies of a stream of fluid or, conversely, to increase the total energy of the fluid stream by applying electrical energy to the system, it is highly desirable, ifnot necessary, to restrict friction losses to a minimum. In electrogasdynamic converters, the friction generated as the fluid flows through the converter channel must be considered for two important reasons. First, friction loss is a measure of conversion efficiency and usually cannot be recouped or preserved for utilization elsewhere. Second, heat energy produced by friction may necessitate cooling of the converter in order to prevent excess temperatures from damaging the converter structure, or in order to aid conversion efficiency by controlling the fluid temperature so that conversion takes place nearly isentropically. It is, therefore, preferable to locate the fluid ionizing and ion collection electrodes at the side of the converter flow channel to reduce friction.

In my copending application, Ser. No. 389,360, filed Aug. 13, 1964, a number of electrogasdynamic converter configurations employing electrodes at the side of the fluid flow channel is disclosed. Certain aspects of this invention relate to or carry forward the teachings of that copending application. In this connection, the present invention provides an improved electrogasdynamic converter characterized by high conversion efficiency, better power density (i.e., higher power output per unit volume of converting apparatus), and a simplified physical design which lends itself well to economic manufacturing methods.

In general, the above improvements are realized by employing a flow channel of generally elongate cross section which may progressively increase in area in the direction of fluid flow such that the fluid velocity in the converter is maintained at a low value. Conveniently, the cross section of the channels may be rectangular. Under subsonic flow conditions in the converter channel, the force exerted on the ionized fluid by the longitudinal channel field tends to constrict the flow path and give rise to fluid acceleration. By expanding the cross-sectional area of the channel the tendency of the fluid to accelerate is counteracted, and the converter can be operated at higher power densities and better ei'ficiency than are achievable with known converters.

In a preferred converter embodiment, the transverse dimension of the channel is maintained constant throughout its length, only the lateral dimension of the channel expanding. The transverse dimension is considerably smaller than in previously proposed converters so that the ion concentration in the ionized stream is as high as possible in order to achieve an optimum electrogasdynamic body force (i.e., the reaction force between the ionized fluid and the longitudinal field in the channel) without precipitating dielectric breakdown of the fluid. The electrode structure in the converter channel takes the form of an array of conductive strips disposed laterally and at the sides of the flow path. Basically, the electrodes in accordance with a preferred form of the present invention are thin film strips of refractory metal or conductive ceramic material superposed on the dielectric interior walls of the channel. In further embodiments, elongate wires or laminated strips, partially embedded in the channel walls, may be utilized.

In further embodiments, the attractor electrodes of an ionizing electrode pair take the form of flat surfaces which extend axially upstream from the end of the channel to form an inlet of greater cross-sectional area (normal to the flow) than the corresponding area of the channel downstream from the inlet. In such case the corona, or discharge, electrode is positioned between the attractor electrode surfaces. For improved ionization efficiency, apparatus disclosed herein may employ a second attractor electrode disposed relative to the corona electrode to effectively increase the axial dimension of the ionizing field set up by the ionizing electrode pair.

In accordance with another aspect of the invention, a plurality of slender channels of the type described above are employed, each providing a parallel flow path for the fluid. In this embodiment, adjacent channels share a common boundary structure, which may be in the form of a substantially flat dielectric plate or a row of spaced conductive wires which serve to shield other channels from induced electrostatic fields. By multichanneling in this manner, the overall length of the converter is substantially reduced and construction is appreciably simpler and less costly than for any electrogasdynamic converter configurations suggested by the prior art, and adequate electrostatic shielding by electrodes or passive conductors allows a large number of parallel channels to be used. When this structure is incorporated into precipitator systems, optimum charge densities can be realized by exhausting the fluid streams into a chamber which is greater in area, normal to the direction of fluid flow, than the combined areas of the channels.

In a related area, the invention also deals with an improved precipitator in which the collecting chamber downstream of the ionizing and dielectric generator sections is provided with an electrically isolated conductor disposed at the interior thereof axially of the flow path. This conductor attains a potential approximating the potential due to the space charge field adjacent the upstream end of the conductor to thereby supplement the transverse electrical gradient throughout the length of the collecting chamber.

For a better understanding of these and other aspects of the invention, as well as the objects and advantages thereof, reference may be made to the following detailed description and to the drawings, in which:

FIG. I is a plan view of an electrogasdynamic converter in accordance with the invention, showing, in addition, electrical connections to the various electrodes;

FIG. IA is a longitudinal cross section of the converter taken along the lines A-A of FIG. 1;

FIG. 1B is an end view of the converter shown in FIG. 1;

FIG. 2 is a cross section of a modified form of the converter shown in FIG. 1;

FIG. 3 is a perspective partial view showing a corona discharge and attractor electrode configuration suitable for use in the present invention;

FIG. 3A is a perspective partial view of another type of corona discharge electrode in accordance with the invention;

FIG. 3B is a perspective partial view of a further embodiment of corona electrode embraced by the invention;

FIG. 3C is a cross section view of the electrode pair shown in FIG. 3, schematically illustrating the shape of a corona discharge ionizing field in the flow channel;

FIG. 4 is a cross-sectional view of a converter channel constructed in accordance with the invention, showing schematically electrical connections for operating the successive stages of the converter channel in series;

FIG. 5 is a cross-sectional view of a converter channel constructed in accordance with the invention, showing schematically electrical connections for parallel operations of successive electrogasdynamic stages;

FIG. 6 is a cross-sectional view of a further embodiment of the invention, employing electrostatic shielding conductors to define a plurality of electrogasdynamic channels;

FIG. 6A is a schematic representation of a portion of the FIG. 6 embodiment helpful in explaining the operation thereof;

FIG. 7 is an elevational view in cross section of an electrogasdynamic precipitation device, employing an improved ionizer construction in accordance with the invention;

FIG. 7A is a cross-sectional view of the apparatus in FIG. 7, taken generally along the line A-A;

FIG. 7B is a plan view of the apparatus shown in FIG. 7, taken generally along the line 8-8 in FIG. 7;

FIG. 8 is a cross-sectional view of an electrogasdynamic converter channel in accordance with the invention, employing a second attractor electrode for increasing ionization efficiency;

FIG. 9 is a partial cross-sectional view of an alternate electrogasdynamic ionizer suitable for use in electrogasdynamic devices according to the invention.

FIG. 1 illustrates a basic electrogasdynamic (EGD) multichannel converter in accordance with this invention. As shown in FIGS. 1 through 18, the converter includes a number of substantially parallel flat plates 12, spaced apart in a fluid guide or casing 14 to divide the working fluid flow into several parallel flow paths 13. The plates 12 may be structurally supported by suitable spacers (not shown) disposed between the plates and elongated in the direction of fluid flow. The direction of fluid flow along the axis of this converter is from left to right, as indicated by the arrows. The plates or channel walls 12, as well as the casing 14, are constructed from a dielectric material such as magnesia, alumina, or boron nitride for higher temperature gases or mylar, lucite, or stycast for low temperature gases. As will be discussed further, the plates 12 may be made from other than dielectric materials which are coated with a dielectric film or sufficient thickness to preclude breakdown under operation conditions in the respective flow paths.

In accordance with the invention, each of the plates 12 in the converter is fan-shaped, i.e., expands from a width w, at the upstream end or inlet 15 of the converter to a width w at the downstream end or outlet 16. The casing itself is of generally rectangular cross section, so that the cross section of each individual flow path, or channel 13, is also generally rectangular throughout its length. Disposed laterally of and at the sides of the respective flow paths 13 are corona discharge electrodes 18 and attractor electrodes 20 situated so as to be substantially flush with the surfaces of the dielectric plates or walls 12. The attractor electrodes 20 have flat surfaces exposed to the interior of the flow paths 13, whereas the corona electrodes 18 comprise a plurality ofsharp, laterally extending parallel edges from which a corona discharge (see FIG. 3C) occurs when a high potential gradient is impressed between the attractor and corona electrodes. A more detailed description of electrode structure will be found in the discussion associated with FIGS. 3-3C. Each plate 12 includes a series of such electrodes, either the corona discharge electrodes 18 or the attractor electrodes 20 (or as discussed later, a combina tion of both) being spaced apart along one side of channel 13 in the direction of fluid flow. In the converter shown in FIGS. 1-18, the first and alternate plates 12 thereafter include six attractor electrodes 20, the intermediate plates 12 containing six corona electrodes 18 in opposed relation to the attractor electrodes 20.

Each attractor electrode 20 and the corona discharge electrode 18 immediately adjacent it comprise a fluid ionizing electrode pair which, when a sufficiently high electric potential is applied thereto, provides an ionization field which ionizes the stream of fluid in the flow paths 13 defined between the respective plates 12. It is seen that consecutive flow paths 13 share a common electrode in each instance. For example, the corona discharge electrode 18 in the second of the plates 12 is common to the top flow path and the flow path immediately below it. Each electrode pair and the downstream portion of the channel defined between adjacent plates 12 may be referred to as an EGD stage, the length ofthe stage being the distance along the flow path between consecutive electrode pairs.

At the downstream end 16 of the converter, each flow path has associated therewith a collector electrode 22 which also extends laterally of the flow path. As in the case of the corona discharge and attractor electrodes, the collector electrodes 22 are substantially flush with the plates 12 at the sides of the flow paths 13. The collector electrodes 22 are similar in construction to the corona electrodes 18 in that each provides one or more sharp edges exposed to the flow path. As will be explained later, however, the function ofthe collector electrodes 22 differs from that of the corona electrodes 18.

The spacing between the plates 12 in a typical converter may be as little as l millimeter; closer electrode spacing renders it difficult to achieve corona discharge in the converter channels without precipitating electric arcing between electrodes. A preferred range of spacing is between approximately 1 millimeter and 5 millimeters, the latter dimension being still small enough to promote good ionization. In this connection, an additional feature of the very thin converter channel is that considerably smaller ionization potentials can be used to excite the electrodes. Spacings as large as l inch may be used for special applications.

FIG. 2 illustrates an alternate form of the FIG. I converter, in which the dielectric plates have been replaced with flowsplitting layers 24 of dielectric wirelike elements 24a. As shown, the elements 24 extend laterally of the flow paths [3 and are generally parallel to the corona and attractor electrodes 18, 20. The attractor electrodes 20 are generally of the same construction as those in FIGS. l-lB, but the corona electrodes 18 in this embodiment are conductive wires. The elements 24a may be, for example, wires such as the corona electrode 18 coated with a refractory dielectric material (e.g., alumina) and are closely spaced (not necessarily touching) along the converter axis. Although the physical surfaces" of the layers 24 are not flat, as is the case with the dielectric plates 12 in FIG. 1, the surface irregularity does not appreciably increase friction losses in the flow path. This is due to the thin boundary layer of flu d established immediately adjacent the surfaces of the layers 24 under subsonic flow conditions, which presents a substantially smooth boundary configuration to the fluid stream. The advantage of this construction is its adaptability to economical mass production.

The wires extend through the sides of the channels (not shown) and connect externally to a circuit providing a reference potential on the wires, and therefore at the sides of the channels. The function of such wires and their external connections are more fully explained in connection with the description of FIG. 6.

ELECTRODE CONFIGURATION FIGS. 3 through 3B illustrate a number of preferred electrode configurations which are suitable for use in EGD converters in accordance with the invention. In FIG. 3, the attractor electrode consists of a thin film strip 25 of conductive material superposed directly on the surfaces 26a of a dielectric wall 26 of the EGD channel. The corona electrode comprises a series of generally parallel, narrow, elongate conductive strips 27 formed on the surface 290 of the opposite channel wall 29. The width of this strip is sufficiently narrow to present to the flow path a line of corona discharge, i.e., a narrow geometric configuration which freely emits charged particles into the flow path when an ionizing potential is connected between it and the attractor electrode stripe 25. The thicknesses of the stripe 25 and the very narrow corona stripe 27 are determined by the conductivity of a material used and the amount of current which the electrode must carry. If the electrode thickness becomes excessive, the electrodes may be recessed into the walls 26 to reduce friction at the side of the fluid flow path.

The attractor and corona electrodes of FIG. 3 can be formed by thin film depositi: n techniques or by spray coating the channel wall surfaces wttn a conductive material. One of the problems previously encountered with refractory material electrodes is their susceptibility to extreme oxidation which effectively coats the electrode surfaces with a dielectric layer which eventually precludes corona conduction between the corona and attractor electrodes. Certain ceramic materials, however, such as titanium diboride and zirconium diboride have sufficiently high conductivity at converter operation temperatures (e.g., in excess of i000 K.) and yet, because they are ceramic, are not sub ect to surface oxidation. Other such materials having the same general characteristic conductivity and suitable for use in electrodes are zirconium carbide, boron carbide, titanium carbide, and vanadium carbide. The walls or plates of the flow channel are preferably dielectric throughout; however, it is possible to achieve good results also by coating the channel walls with dielectric material. High conductivity ceramic materials such as those noted above may be applied to dielectric materials (e.g., alumina or boron nitride) by spray coating, thus permitting rapid and economic formation of the electrodes. A foremost advantage of clec trodes constructed from thin film conductive material is that, in conjunction with the expanding channel, the overall lateral and axial dimensions of the converter are reduced while, at the same time, high isentropic efficiency is preserved.

FIGS. 3A and 3B show alternate forms of electrode construction. In FIG. 3A, the attractor electrode 31 is a single bar of conductive material laminated in the EGD channel wall 26. The corona electrode comprises a plurality of flat laminated strips 32. interposed between dielectric sections 33 and disposed transversely of the wall 29. The strips 32 have sharp edges 320 which are substantially flush with the channel wall surfaces 29a for exposure to the fluid flow and present a line of corona discharge thereto. in FIG. 3B, the corona electrode comprises several parallel thin wires 34 which may be at least partially embedded in grooves 35 in the channel wall 29. Any of the above electrode forms provide satisfactory and efficient fluid ionization and lend themselves well to mass production manufacturing.

FIG. 3C illustrates the approximate shape of the corona discharge field 37 under the influence of fluid flow between the electrodes of the type just described. As shown, when an ionizing potential, represented by the battery 39, is impressed across the corona and attractor electrodes 39, 40, an electric field extends transversely of the flow channel in which ions 42 are produced and carried downstream by the fluid. Although the corona electrode shown comprises only three conductive strips 39, it is understood that higher corona discharge densities in the electric field 37 may be obtained by employing additional such strips, closely spaced.

Returning to FIG. 1, representative electrical connections to the converter are shown. A voltage dividing network 44 is connected between the corona discharge electrodes 18 of the first stages and the respective collector electrodes 22 which are also electrically coupled together, as shown in FIG. 1A. ln keeping with the desirability of compactness and higher power output per unit of converter volume, the voltage divider 44 is a thin film stripe of resistive material superposed on an outside surface 45 of the casing. The film may be either a refractory metal or conductive ceramic material such as zirconium diboride. For purpose of illustration, a load 44a is shown connected across the converter output, in parallel with the voltage divider network 44. The attractor electrodes and the corona discharge electrodes 18 of the following stages are similarly electrically connected together, as best observed in FIG. LA, by the conductors 46 and 48, respectively. A voltage source 49 is connected via a switch 490 to the first or upstream ionizing electrode pairs. The attractor electrodes of the following stages are connected to taps 50 on the voltage dividing network 44 by the conductors 46a46e which terminate on adjustable contacts 51. The taps 50 are preferably located on the network 44 so that the axial field E, created in the channel when the converter is operating is substantially linear.

The positionable contacts 51 on the voltage divider network 44 provide means by which the potential applied to the respective pairs of ionizing electrodes may be set to obtain the correct ionization voltage for each EGD stage. lt is, of course,

desirable that all of the ions (positive or negative) injected or created by ionization at the first EGD stages arrive at the collector electrodes 22. However, owing to the space-charge-induced fields in the respective flow paths 13, the ions experience an electrostatic force which tends to drive them to the sides (plates 12) of the EGD channel. The intermediate electrode array, therefore, compensates this deposition of ions by replenishing the fluid stream with ions produced in the ionization field. However, by properly adjusting the ionization potential, the ion concentration in the fluid stream can be controlled to be in maximum permissible proportion to the fluid density. This, in turn, is accompanied by an EGD body force which is also maximum, and conversion efficiency is therefore optimized. These facts will be better appreciated in the subsequent theoretical discussion.

OPERATION OF THE ELECTROGASDYNAMIC CHANNEL For purposes of explanation, FIG. 4 illustrates a single EGD channel of the FIG. 1 converter, like elements being designated by the same numerals used in FIG. 1. In brief, operation of the converter is as follows: A working fluid such as a combustion gas from a source (not shown), flows through the channel from left to right, as indicated by the arrows. When the switch 49a is closed, the corona discharge electrode l8 is biased negatively with respect to the attractor electrode 20 by the voltage source 49, and a corona discharge field 53 of the type shown in FIG. 3C is established between these two electrodes, thereby injecting electrons into the stream to form low mobility negative ions 54. Those ions 54 are swept downstream by the fluid and travel across the channel under the action of the space-charge-induced electric field which exists in the channel due to the presence of charged particles. Some, but not all, of the negatively charged ions deposited at the side of the channel are neutralized by the attractor electrode 20a; the remainder of the charge-carrying ions are blown further downstream to subsequent attractor electrodes 20b-20 and the collector electrodes 22. To the extent that the attractor electrodes 20a20e neutralize the charge deposited at the channel wall 12, they are also collector electrodes.

When negatively charged particles reach the surfaces of the attractor electrodes 20:: 20e, the negative charge (electrons) finds a path through the external voltage divider network 44 to the first corona discharge electrode 18. This flow of electron current establishes a potential buildup across the voltage divider network 44 which is progressively more negative at the downstream taps 50. ln this manner, the voltage divider network and the attractor electrode connections thereto allow the initiation of EGD conversion by one or more starting potentials which are considerably less than the steady-state operating potential between the electrodes 18 and 22.

With the movable contacts 51 positioned downstream of the respective taps 50, each of the corona electrodes l8a-l8e is impressed with a voltage which is negative relative to the associated attractor electrodes 20a20e, and each electrode pair is biased to sustain an ionizing field in each EGD stage. The intermediate electrode pairs l8a20a-l8e20e replenish the negative charge lost by deposition on the sides of the channel and neutralization by the attractor electrodes 20a- -20e. Because of the ion reinjection, most of the charge current injected into the flow channel by the source 49 finds its way to the collector electrodes 22 at steady-state conditions. Moreover, with a proper adjustment of the movable contacts 51 on the voltage divider network 44, the ion concentration n in the channel can be controlled so that it is proportional to the density of the fluid, thereby maintaining the induced electrostatic (space charge) field at the desired value. For maximum efficiency, this field is kept to a value very close to the breakdown voltage E, of the ambient medium (e.g., air) surrounding the converter.

Owing to the increasingly negative potential of downstream electrode pairs, ions forced through the channel by the fluid gain electric potential energy. since work must be exerted on the negative ions 54 in overcoming the repelling longitudinal field E, existing in the channel This work is supplied from the kinetic and thermal energies of the fluid. Thus, energy is extracted from the fluid and converted into electrical energy. The negative charge neutralized by a collector electrode 22 takes parallel paths-one through the voltage divider network 44 to provide a bias potential across the last electrode pair l8e 20, and the other through the high impedance load 440 where the electrical energy is utilized.

As previously noted, the corona and collector electrodes differ in function although they are similarly constructed. The collector electrode 22 "collects" or neutralizes the negative ions 54 by, in effect, emitting positive ions, whereas the corona electrodes 18a-l8e ionize the fluid by an emitting negative charge. If the polarity of the voltage applied to the ionizing electrodes were reversed, the same would hold true, except that the corona electrodes would then emit positive charges and the collector electrode negative charges.

It should be noted that the conversion process just described is reversible. That is, if a high voltage source of the polarity shown were substituted for the load 44a and the connections to the electrodes reversed so that positive ions would be injected into the fluid stream, the EGD converter acts as a fluid pump whereby the fluid is accelerated through or compressed in the channel. In this case, the "body force" is the attractive force exerted on the fluid by the longitudinal field E,, Ions collide with fluid particles as they travel through the channel, bringing about a viscous coupling which drags the fluid toward the collector electrodes 22.

In FIG. 4, the electrical connections to external circuitry are such that successive stages of the EGD channel (each stage including one corona and attractor electrode and the downstream length of the channel to the next electrode pair) is in series; that is, the charge carrying ions viscously coupled with the fluid increasingly gain potential energy as they are propelled downstream to the collector electrodes 22. HO. 5, on the other hand, depicts a single EGD channel connected for parallel operation so that the output current, but not the voltage between successive stages, increases as the chargecarrying particles are carried downstream. In this channel, the corona electrodes 56a-56d alternate with the attractor electrodes 5812-5811 at each side of the channel. Thus, the attrac tor electrode 580 of the first electrode pair is in the upper plate 60; in the following electrode pair it is in the lower plate 62, and so on. As in FIG. 4, the corona electrodes 560-561! are in opposed relation to the attractor electrodes so that the ionizing field extends transversely of the channel flow path. Upon closing the switch 63, the first and alternate electrode pairs thereafter, 56a-58a and 56c58c, are biased by the potential source 64 to yield negative ions 65 to the stream. When the switch 66 is closed, a potential from the source 67 is applied to the remaining electrode pairs S6b-58b and 56d- -58d. Since, however, the corona electrodes 56b, 56d are positive in potential relative to their associated attractor electrodes 58b, 58d, positive ions 69 rather than negative ions are produced.

As the ions are swept downstream by the fluid (flowing from left to right), they move toward the sides of the flow path due to space charge effects and intercept the corona discharge or ionization field of the next stage where they are neutralized by the charge of opposite polarity in that field. lt should be noted that in this configuration, the electrodes 56a56d are both collector and corona electrodes. That is. when a negatively charged particle 65 arrives at the longitudinal position of, for example, the electrode 56b, it is neutralized by the emission of a positive charge 69 from that electrode and passes into the external load 70. At the same time, however, positive ions 69, in sufficient quantity, are continuously created by the positive corona discharge between the electrodes 56b and 58b so that the charge in the next EGD stage is constituted of primarily positive ions. This sequence of events is identical for all stages; if follows that the currents are additive through the load 70.

Since alternate stages conduct charges of opposite polarity, and since such alternate stages are connected in parallel by the external circuit, they are also in parallel internally, and the voltage generated in one stage is followed by a generated voltage of opposite polarity, relativeto the respective corona electrodes, in the next consecutive stage. This is because in one stage, negative charges are being moved against a negative field and in the next stage, positive charges buck a positive field.

By arranging successive stages in parallel as shown in FIG. 5, the electrical impedance of the EGD generator (or the EGD pump as the case may be) is reduced. (For operation as a fluid pump or propulsion. a modification of connections similar to those outlined for the FIG. 4 circuit is made; viz., the load 70 is replaced by a voltage source and the polarity of the voltages from either the source 70 or the sources 67, 64 reversed.) The minimum voltage per stage is determined by practical considerations such as minimum electrode size and their spacing in the same plate. The closer the electrode spacing between consecutive stages, the lesser the generated voltage. It has been found that voltages as small as 10,000 volts can be produced at lower efficiencies, but 50,000 volts per stage is more practicable. W

THEORY AND DESIGN FACTORS It was earlier briefly noted that in converters in accordance with the present invention, the ion concentration n can be controlled for optimum converter efficiency. That is, the ratio of the EGD body force to the friction force is maximum for any given fluid velocity.

The longitudinal electric field E, is maintained uniform along the channel by choice of suitable bias resistances in the external voltage divider network. Preferably, it is maintained at a value that is convenient to handle in the external circuit; for example, 3X10 volts per meter which is the breakdown strength of air at standard temperature and pressure.

The ratio of friction-force ie, the force opposing fluid motion) to the EGD body-force f (ie, the force supplied by the fluid in moving ions against the field E in the case of an EGD generator) is given by the relation where c; is the coefficient of fr ction. p is the fluid density, u is the fluid velocity, s is the ptil'l'lltl fi; of free space, E, is the uniform longitudinal electric field, which is maintained just below the breakdown strength of the ambient air E,=I; =3X l0 volts/m., and E, is space-charge induced electric field normal to the walls of the channel. E, is proportional to the ion concentration n in the channel and is limited by the breakdown strength E of the gas, which in turn is proportional to the density p; therefore, let the ion concentration n be adjusted such that v Eb=Ez;(P/P) where the bar denotes standard pressure and temperature conditions.

With the ionizing electrode circuit adjusted to inject sufficient current to keep the ion concentration n at its maximum allowable value (Expression (2)), it is possible to evaluate Expression (2) under a typical set of subsonic flow conditions. For example, assuming the following conditions:

u=50 m./sec., the friction to body force ratio becomes 1 Cf F112 In this situation the local isentropic ffiCll1C of the channel IS 1 o f. b (3) This value is relatively high and much larger than achievable with known converters. Specifically. the attainment of high efficiency results from (I restricting fluid motion to moderate velocities and (2) reducing the coefficient of friction through employment of special electrode construction.

It can also be shown by integrating the generalized gasdynamic equations for the constant velocity expanding channel that the relationship between an axial position in the channel and Mach number is given by E f i I('Y" "(fI' fb) where x is the distance from the position where sonic conditions would occur, M is the Mach number, y is the specific heat ratio, and h is the height (transverse dimension) of the channel.

The cross-sectional area A and the width of the channel w are also found from integration to be related to the Mach number where the asterisk denotes sonic (M=l conditions.

Since the flow is approximately isentropic, we can write for the other gasdynamic variables the following approximate expressions for These formulas are very useful in the design of EGD generators and pumps of this type. By way of example, let us assume that we are to design an EGD generator having an efficiency of 50 percent, operating on a combustion gas having the following inlet conditions:

M l 0.0745 Using the foregoing gasdynamic formulas (6)( l l the exit conditions after extracting 50 percent of the total enthalpy are:

p,,=2 92 atmospheres it an, Was, (12

where it has been assumed that the ion mobility is FI (1 4 k, m /volt-sec. (13) Thus, in practice, the minimum voltage that can be extracted from a single stage under the above set of conditions is If the ion mobility is higher than this assumed value at standard temperature and pressure (k,=l0rn'/volt-sec.), then the aspect ratio I/h of a single stage is smaller, more stages are required, and a lower voltage can be extracted per stage.

Continuing with the above, assuming '1': 1mm., the dimensions of the channel (see FIG. 1) can be determined from the foregoing expressions. These dimensions are:

h=l0" meters L=3.59 meters I=17 mm.

w =meter w,,=meters.

Each channel, therefore, contains L/I=2l 1 stages and the power output is 10 watts.

It is additionally significant that the current in each stage is also constant, since it is given by the formula Fen uh w, (15) and the ion concentration n is proportional to the density p, while the width w of the expanding channel is inversely proportional to the density. It follows that the power extracted by each stage is also the same.

Because the thickness of each dielectric channel wall or plate can also be reduced to as little as I millimeter, l0 megawatts of output power can be generated by multichanneling the converter with of these channels. The total height of the converter channels is then H=100X0.002=02m. and the total volume occupied by the assembly is approximately 1.08 m The power density of this assembly is therefore approximately 10 watts/m Another very important aspect of this system is that because of the attainable isentropic efficiency no coolant need be used to restrict fluid temperature and the converter can be used at isolated locations where there is often no available cooling fluid such as water. Moreover, the converter may operate on any of a number of gases, including natural sources of wet steam from geothermal streams, to generate commercially distributable power at the situs of natural energy sources.

ELECTROSTATIC SHIELDING In describing FIG. 2, it was mentioned that rows of wires dividing adjacent flow channels may be connected to an external circuit to provide on each wire conductor a reference potential. These wires, however, have the further important function of establishing a reference potential that prohibits formation of excessive electrical fields and potentials at the flow path boundary which might precipitate dielectric breakdown of the gas or channel components and cause damaging arcing. The wire conductors, therefore, also tend to shield each channel from space charge potentials and fields induced by other adjacent and nearby channels.

It should be recognized that the space charge field gradient within an enclosure serving as an electrogasdynamic channel is dependent upon the space charge concentration and the distance over which such concentration is present Thus, if several such channels are disposed in closely ad acent relation, space charge fields in each channel induce a space charge field in adjacent channels and, absent any other provision for interchannel shielding, those space charge fields can be neutralized or cancelled only by an induced space charge field having an opposing effect. It is apparent, moreover, that the outer channels in a stack or array of parallel flow channels, such as that indicated in FIGS. 1-18, tend to operate under a substantially higher transverse space charge field than those channels at the interior of the array Thus, if each electrogasdynamic channel is independently operated near maximum tolerable limits of space charge concentration. it is possible that the breakdown electric field threshold will be exceeded in at least the outer parallel flow channels.

In addition, the dielectric surfaces of the channels tend to hold electrical charges contacting them and may acquire a surface charge concentration sufficient to precipitate arcing within the channel.

To a certain extent, such adverse effects of induced space charge fields can be minimized by, for example, spacing the ionizing electrodes at short axial distances and biasing axially adjacent electrodes at potential differences well below critical values. In such case, the ionizing electrodes function to provide terminal points for the electric space charge field, thereby limiting the maximum distance over which any space charge concentration can act. This expedient, however, may prove impractical for long channels, requiring an excessive number of electrodes. In FIG. 2, the shielding wire conductors are dielectrically coated, thereby preventing electrical discharge of any ions or charged particles contacting the wires after being driven to the flow boundary by aerodynamic and space charge effects, but improved results are obtained by employing bare conductive surfaces and using the dielectric properties of the gas to isolate the channels. The apparatus of FIG. 6 incorporates the latter solution to this problem, and carries forward the techniques disclosed in my copending application Ser. No. 756,220, filed Aug. 29, I968.

Referring to FIG. 6, a series of parallel electrogasdynarnic conversion channels are formed between adjacent axial rows of rigid, exposed electroconductive (e.g., metal) rods 70. Each row of rods may be considered a flow boundary for a thin electrogasdynamic channel bounded by an adjacent row of rods. It is not, however, essential that the rods of each row be so closely spaced as to form a continuous boundary layer for the establishment of laminar flow, as the device may also be considered as a single channel having an array of conductive rods effective to set up the desired potential distribution, as will be explained. It should also be remarked that although the rods are conductive, the gas may be considered a dielectric medium such that the rods effectively establish a dielectric guide for the flow. For the purpose of explanation, each electrogasdynamic channel (formed by adjacent rows of rods) is connected to operate in the manner described in connection with FIG. 5, with each channel shown to contain three stages. The length of each stage is determined by the axial distance between the ionizing electrodes 72, 74 of each channel, with the last stage shown terminating in electrodes 76 similar to the attractor electrodes 72, but functioning as collector electrodes. It should be observed in this case that a single corona electrode 74 is located intermediate and establishes a corona discharge field to each of, two adjacent attractor electrodes 72.

The entire assembly, including the channel-defining rods 70, the ionizing electrodes 72, 74 and supporting structure is housed in a suitable pressure vessel 78, which may assume the diverging shapes of the apparatus of FIGS. 1-18 so that the lateral dimension of the channels progressively increases from one end of the device to the other. The attractor electrodes 72 for the first and third stages are connected through suitable conductive elements 79 to the metal wall of the vessel 78, with the attractor electrodes 72 of the second stage (serving also as the collector electrodes for the first stage), together with the collector electrodes 76, interconnected through insulated terminals 82 to a high voltage output conductor 84 Gaseous flow through the assembly is indicated by the direction of the arrows. The corona electrodes are connected to a potential source in the manner shown in FIG. 5. A dielectric coating at the vessel interior isolates the vessel walls from the charges cam'ed by the flow.

All rods 70 at a common axial location in the channels are connected through conductors 85 to a common point on an external resistive biasing network 86, thereby establishing for all channels a reference potential within the channel, and a maximum potential difference between any of the axially spaced rods 70. Preferably, the network constitutes a high resistance film on a sidewall of the fluid guide vessel 78 which, if desired, may be grounded, as shown. Connections of the network 86 to the rods 70 are then made by physical contact of the rods with the resistive fiim.

With the construction of FIG. 6, the rods serve the dual function of establishing within each channel a uniform applied electric field along the length of the channel and of neutralizing the interchannel induced space charge fields by providing closely spaced terminal points (at selected potentials) for the space charge fields. Any charged particles or charges striking the rods 70 become discharged, with the charges being conducted through the external biasing network 86. Current through the rods 70 is effieientl y utilized in the external circuit 86 to maintain a desired potential on each rod and thereby also to maintain a uniform axial electric field gradient within the flow paths. The use of bare conductive elements such as the rods 70 also reduces the previously experienced problem of excessive buildup of electrical charge concentration at the dielectric boundaries ofthe conversion channels.

It is immediately apparent that maximum effectiveness of the conductive rods 70 in shieicing channels from induced space charge fields from other channels is obtained by making the spacing between rods as small as possible. However, this leads to larger, and perhaps inefficient, pressure drop in the channel due to viscous drag. By and large, therefore, optimum spacing of the conductive rods is determined by the space charge concentratier. within the device and the maximum distance by which such rods car be spaced without incurring dielectric breakdown. Although the rods 70 in FIG. 6 are shown of circular cros section, other cross-sectional configurations, such as an ellipse, may be used to reduce aerodynamic drag Referral to FIGv 6A may be helpful in better understanding the manner by which the rods 70 limit the maximum space charge field in the channels. FIG. 6A shows in cross section a few rods 70 at any location in adjacent channels. Each rod 70 is spaced a distance it from the most closely adjacent rod (on a diagonal) so that the transverse height of each channel between rows of rods is The foregoing geometrical arrangement is used for purpose of explanation and ease of computation only and should not be taken as critical or preferred. An arbitrary imaginary enclosure in the form of a square 90 may be drawn to surround each rod to designate the boundary in space of all electrical charges inducing a surface charge on each rod. The boundary is drawn so that it falls midway between any two rods 70 in order that the same area is obtained for each enclosed area.

The area .4 of unoccupied space within each square, from inspection,

If the particle concentration in the flow is assumed uniform at N,, with each particle having n, charges of e (an electronic charge), then the total charge Q, per unit length of each volume having an area A is:

By GAuss' Law, an equal image charge appears on the cylindrical surface of the rod 70, the area Q, of which is a,.=21rr. The total surface charge per unit length is therefore the product of area and surface charge density 11, or:

where E, is the electric field at the surface of the rod due to the surface charge The quantity E, is also equated to the space charge field at the rod.

Since Q,=Q for the assumed geometry, expressions (l7) and (18) may be equated;

From expressions (20), it can be seen that the maximum space charge E, at any point in the channel is directly related to the rod (conductor) spacing h. When h is made smaller, the space charge is reduced by a corresponding amount, and as charge concentration en N increases, the spacing h must be made smaller for any given space charge field E,.

An important feature of the embodiment of FIG. 6 is the axially staggered location of the conductive rods in adjacent channels. With the rods 70 staggered, as shown, the electric field established between any rod of one row and the closest rod of an adjacent row has both axial and transverse components. The transverse component of the electric field, however, alternates in polarity from one rod 70 to the next. A corresponding alternation of the electrostatic force on any particle moving between any two adjacent rows of rods, therefore, will occur as the particle moves downstream. This alternation of the electrostatic field force on the particles tends to keep them within the boundary defined by the rows of conductors and thereby prevents their tendency to drift out of the respective channels and into the planes of the rods. Fortunately, turbulence and flow separation around the rods tend to counteract this effect and, therefore, although the staggered array of rods is preferred, it is not necessary.

in a properly designed channel, where both the axial electric field opposing downstream motion of the charges and the maximum space charge field between adjacent rods are proportional to gas density, it can be shown that the relative current loss to the rods is independent of space charge concentration. Moreover, the ratio of friction force to electrical force on the rods is inversely proportional to density; therefore greater space charge concentration may be used with greater effectiveness in achieving high isentropic efficiency. This is because as space charge concentration increases, friction forces consume a less significant proportion of the total energy expended.

Under typical conditions, the Reynolds number R of flow may be approximately 10; therefore, it can be predicted that gas flow separates from the rods directly exposed to the gas flow. Accordingly, very few charged particles may be expected to diffuse to the downstream profile surface of the rods. Thus, in general, only the upstream profile surface of the rod collects an electrical charge and that charge, if carried by a solid particle, discharges to the rod, removing the attractive electrostatic forces tending to hold the particle on the rod. Therefore, the front profile surfaces of the rods tend to remain clean, although particles are observed to collect in the stagnation zone at the rear, or downstream profile surface of the rod.

in experiments conducted with the type of device shown in FIG, 6, current losses due to precipitation of charges to the bare metal rods was found to constitute less than 2 percent of the total current carried by the channel. In these experiments, the spacing between rods was 2 cm., the radius of each rod was 5 mm., the length of each channel stage was 30 cm., the maximum electrical field E, within each channel was volts/meter and the gas velocity was 30 meters/sec.

ELECTROGASDYNAMIC PREClPlTATOR IMPROVEMENTS Turning to FIG. 7, there is shown an improved electrogasdynamic precipitator in accordance with the invention. In principle, this precipitator operates in an identical manner to the precipitators disclosed in my copending application Ser. No. 477,5l6, filed Aug. 4, 1965 for "Precipitator Systems," In accordance with the present invention, however, the ionizing section of the precipitator includes dielectric fluid guide means comprising generally a series of spaced parallel dielectric plates 130 which are contoured at the upstream and downstream ends to form a converging inlet 131 and a diverging outlet 132 between each of the plates 130. Extending axially in the upstream direction from the ends of the plates 130 are substantially flat conductive plates 1320, with adjacent plates forming between them an inlet for each of the flow channels 130a defined between adjacent plates 130, As shown, the cross-sectional area of these inlets normal to the flow path is greater than the corresponding cross-sectional area of the flow path downstream thereof. The plates 1320 form attractor electrodes for attracting an ionizing discharge.

Disposed between the attractor electrode plates 1320 are several closely spaced corona discharge wires 133 arranged in a planar configuration generally parallel to the plates 1320. Together, the corona discharge wires 133 and the attractor electrode plates 132a form an ionizing electrode pair for establishing an ionizing, or discharge, field at the inlets to the respective flow channels 130a when an electrical ionizing potential source 134 is connected between the attractor and corona electrodes, as shown in FIG. 7A.

The entire ionizing and flow channel assembly may be supported in a suitable conduit 136, as best seen in FIG. 7A, which in turn is suitably secured to the wall of the collecting chamber 138. The corona discharge wires 133 are passed through small holes bored in the sides of the supporting conduit 136 and held in place by retainers 137 at either end of the corona wires. The supporting conduit 136 may be metal, as depicted, and one terminal of the ionizing source, here represent by the battery 134, may be connected directly to the conduit 136, the other terminal of the source 134 being connected directly to the several corona discharge electrodes 133. Located downstream of the dielectric plates is a collecting chamber, or collector electrode, 138.

The collector 138 is preferably constructed from a metallic material and is also preferably (but not necessarily) cylindrical. If desired the collector surface 138a may be constituted of a dielectric coating to prevent electrical discharge of the particles reaching the collector 138. In such case an electrostatic force on the particles tends to hold them to the surface 138a and thus reduce their reentrainment. It is additionally desirable to have the cross-sectional area (normal to the flow path) of the collector 138 larger than the combined corresponding cross-sectional areas of the individual flow paths defined between the dielectric plates 130. ln such case, the velocity of the gas entraining the particles to be precipitated is decreased, thereby giving the particles a longer residence time in the collector and enhancing the probability that the space charge field in the collector will force them to the wall of the collector, where the particles are precipitated. Upon reaching the wall of the collector 138, the particles, if they are heavy enough, are free to gravitationally descend downwardly along the collector inner surface 138a and out of the precipitator through the annular exit formed between the collector 138 and conduit 136.

From the foregoing, it will be apparent that as the gas containing the undesired particles is flowed through the conduit 136 and into the inlets of the flow channels, the entrained particles become charged by the ionizing field established between the corona and attractor electrodes 133 and 1320, respectively, and are carried farther downstream by the dynamic forces of the gas stream, guided by the flow channels 1300. The collector electrode 138 may be connected externally to ground or, alternatively, through an external load. It

will be further recognized that the dielectric plates I30 isolate the charge flow from external electrical circuits and form an electrogasdynamic converter, or generator. section in which the potential energy of the charged particles is raised at the expense of the kinetic energy of the fluid stream, since the stream exerts a force in pushing the fluid and particle mass downstream against the axial field existing between the ionizing electrodes 1320, 133 and the collector electrode 138. This potential energy, of course, appears as a space charge potential field within the collector section. 7

An additional function of the dielectric converter section of the precipitator, i.e. the dielectric plates 130, is to direct the electrical image force between the emitted charges and the flow channels. Without the dielectric plates 130, every charge emitted from the corona electrode would produce an image charge that would remain in the metallic attractor electrodes. Then the charge released from the corona electrode, as it began to travel downstream, would set up an intense electrical field between it and the image charge at the attractor electrodes, thereby creating an axial electric field that is productive of a force retarding motion of the charges in the downstream direction. Such retarding force adds to the axial field in the converter section and thereby increases the energy which must be exerted by the fluid in order to move the particles downstream to the collector section. Moreover, if the space charge density immediately downstream of the ionizing electrodes is high, as is desirable for maximum efficiency, the image charges will be drawn out of the attractor electrode to neutralize the space charge. This flow of image charges appears as arcing or dielectric breakdown within the flow channel. On the other hand, in the structure shown in FIG. 7, the image charges are located in the dielectric plates 130 so that the electric field lines from the charges in the fluid stream terminate on the image charges in the dielectric plates. These field lines will therefore always be normal to the direction of flow and produce no additional retarding force on the downstream motion of the charged particles.

In HO. 7, the charge concentration in the collector section may be efficiently increased up to the maximum permissible concentration for a radial space charge field just less than the field required for dielectric breakdown of the gas by injecting into the particle-laden gas smaller particles to be charged by the ionizing field in the flow channels. By properly selecting the size of the injected particles, the charge acquired by the particles, and therefore their mobility, can be controlled within permissible limits. These injected particles, which may be either liquid or solid, form a charged aerosol which is carried downstream by the gas into the collector 138, thereby increasing the charge concentration in the collector and strengthening the space charge field. Moreover, these particles are precipitated from the stream along with the undesired particles so thatthe gas exiting from the outlet of the collector is clean. Means for injecting the aerosol particles is represented schematically in FIG. 12 by the series of nozzles 140 which spray the aerosol particles into the inlet of each flow channel between the attractor electrodes 132a.

THEORY AND DESIGN FOR PREClPlTATOR SYSTEMS It can be shown that the highest space charge potential, relative to the potential at the surface of the collector, appears at the collector axis and is given by the following relation:

v n 5&

The space charge field E, at the surface 138a of the collector is defined by the following equation:

For any given concentration of particles of known size, therefore, the radius R of the collector 138 is ideally:

2e E, en N amas L12 as, 4 2

The efficiency of collection of charged particles has been derived in the previously mentioned copending application Ser. No. 477,516, and is:

1+ q/xo where h is given by x e u,

K en N in which u is the gas velocity and K, is particle mobility.

Assuming that percent collection efficiency of charged particles is desired, the effective length of collector L can be determined. Thus,

K en N Combining expressions (24) and (28), we obtain an expression governing the aspect ratio L /R of the collector section of the precipitator:

Higher collection efficiencies, of course, can be obtained by designing the collector section with a larger aspect ratio or, as explained earlier, by seeding the gaseous stream with submicron size particulate matter, which is easily charged to saturation, for augmenting the space charge field.

Since a transverse space charge field is present in the generator section (between the dielectric plates as well, some deposition of charged particles to the surfaces of the dielectric plates tends to take place. For purposes of explanation, we can assume that the velocity u of the gas through the generator section should be high enough so that not more than 5 percent of the charged particles reach the surfaces of the dielectric plates. (it may be remarked that with sufficiently high gas speeds, these few particles become rapidly reentrained in the flow path with very little resultant charge loss.) From expression (26), less than 5 percent of the charged particles will be deposited on the surfaces of the dielectric plates 130 if From the foregoing, it follows that the ratio of the gas velocity :4, in the generator to the velocity u, of the gas in the collector for 90 percent collection efficiency should be uc 2 L. 2 (32) Having determined the gas velocity ratio, the total crosssectional area of the flow paths defined between the dielectric plates I30 can be determined, since the gas flow rate through the collector I38 and the radius of the collector have been selected for any given maximum particle concentration.

As a design example, we may consider a typical precipitator for removing dust particles having a concentration of about l grains/ft: and a mean diameter of about microns. The average particle concentration at this dust loading is approximately 2XlO' particles/m It is known that the particles of any given size can hold only a maximum (saturation) charge. In the present example, taking a realistic assumption that the particles are charged to 50 percent of saturation, the particle mobility is K,,=l0"m./volt sec. and the number of charges per particle N,=3 l0.

Under the foregoing conditions, the ideal radial dimension R of the collector (from equation (24)) will be 0.55 meters for 90 percent collection efficiency in the collector. The value of L may be determined from expression (27) and is calculated to be 0.83 14,. Typically, the velocity of the gas in the collector is about 5m./sec. (equivalent to a flow rate of l0,0()0 c.f.m.) and, thus, L =4. l 5 m.

The maximum potential ofthe space charge in the collector is found from expression (2l) to be approximately 800 KV and the required generator length L,, i.e., the length of the dielectric plates 130, is therefore L,=0.28m. From expression (32), the velocity u, of the gas in the generator section flow channels is calculated to be u,=56 m./sec. Knowing the desired velocity of the gas through the flow channels and the charge concentrations, the number and dimensions ofthe flow channels can be selected. Generally, this will also involve a consideration of the spacing between the corona and collector electrodes 131, 1320 such that the required voltage for ionization of the gas is ofa practicable value.

PRECIPITATOR COLLECTOR Referring again to FIG. 7, the space charge field If, at downstream locations in the collector 138 can be substantially increased through the use ofa passive central conductive electrode I42 which is preferably coaxial with the collector I38. This passive conductor 142 is suitably supported to have its downstream tip I420 exposed to the charges exiting from the flow channels in the generator section. The conductor I42 is supported by the radially extending arms I43 attached to the wall of the collector I38 and surrounded by a dielectric material layer 144. As the flow of charges begins to build up the space charge potential at the axis of the collector 138, the induced electrical potential P on the conductor I42 also increases, since the tip l42a is exposed to the gas flow.

Ultimately, the potential on the conductor 142 will attain the value of the space charge potential in which it is located. This potential, of course, appears throughout the length of the passive conductor so that the space charge field downstream of the tip 1420 will be increased by the electrical field gradient established between the charged conductor I42 and the surface 1380 of the collector. It is also possible to apply a supplementary potential to the conductor 1420 from an external source 145, and to eliminate the dielectric coating I44, if desired. In either case, although the radial space charge field gradient decreases in the downstream direction as the charges are neutralized at the collector wall, a minimum electrical field gradient normal to the flow path will still be present due to the charges on the conductor I42.

IONIZING ELECTRODES OF FIG. 8

FIG. 8 illustrates an alternate arrangement for ionizing the gaseous flow in the flow channel. As shown there, the main flow channel between the dielectric plates I46 is subdivided into two secondary channels I47 by an intermediate flow dividing plate I48. Attractor electrodes I49 are positioned at either side of the main flow channel to be exposed to the fluid flow, and the corona discharge wire electrode 150 is disposed transversely of the flow path intermediate the attractor electrodes I49 in a gap 151 in the flow dividing plate I48. Located downstream of the attractor electrodes 149 in the plate I48 is a second attractor electrode I53 having surfaces I530, 153!) exposed to the flow in the secondary channels 147. A high direct current potential, represented by the battery 154, is applied between the corona wire 150 and the second attractor electrode I53, and also across a voltage dividing potentiometer 155. The positionable contact a ofthe potentiometer is coupled directly to the attractor electrodes I49.

In practice, the positionable contact I551: is set to yield a corona discharge between the corona wire 150 and each of the attractor electrodes 149. Since, however, the second attractor electrode I53 is at a higher potential than the electrodes I49, the charges drawn from the corona electrode 150 by the ionizing potential between it and the attractor electrodes 149 are attracted in the downstream direction to a second attractor electrode I53. It may also be remarked here that the second attractor electrode may be replaced with a thin wire similar to the corona wire I50, if desired, and the corona electrode may be ofdiffcrent form, such as those illustrated in FIG. 3.

With the electrode arrangement of FIG. 8, the axial dimension of the effective ionizing field, i.e., the region in which ionizing current is present, is effectively lengthened by the axial distance between the attractor electrodes I49 and the second attractor electrode 153. Concomitant with this axial extension of the ionizing field is an increased probability of the entrained particles becoming fully charged due to the increased residence time of the particles in the ionizing field.

It can be proven that the effect length b of the ionizing field between the extremes of the first and second attractor electrodes in a flow channel of minimum cross-sectional dimension h should be such that b/hZS. Where the density of the gas in the flow channel is large, the current required for charging the entrained particles to saturation is also increased. This current can be obtained by increasing proportionately the strength of the ionizing field, the ratio b/h remaining unchanged. Ideally, of course, b/h=3, since by increasing the ratio b/h by moving the second attractor electrode 153 downstream, a higher potential must be applied between this electrode and the corona electrode.

IONIZER COOLING In cases where the temperature of the working gas flow is high, cooling of the flow in the precipitators or converters discussed may be accomplished by passing a coolant through the ionizing section. FIG. 9 represents a partial cross section of a typical ionizing and generator section 92. The section 92 is seen to include dielectric plates 920, each provided with a corona electrode 93, and an attractor electrode 94, both of the type shown in FIG. 3A. Extending laterally of and at the interior of the dielectric plates 92a are several cooling passages 96 through which a suitable coolant, such as water, is continuously passed for maintaining the plates 92a at a low temperature. In this manner, a substantial reduction in the temperature of the gas flowing between the plates 92a can be effected, at the same time raising the potential energy of the particles charged in the ionizing field between opposed corona and attractor electrodes 93, 94.

Iclaim:

I. Electrogasdynamic converter apparatus for ionizing a stream of fluid comprising:

fluid guide means having a inlet and outlet and means for establishing therebetween a flow path boundary configuration for the stream when the stream is passed therethrough, the boundary configuration having a substantially elongate cross section;

first electrical discharge electrode means disposed at a side of the flow path so as to be substantially flush with the immediately downstream portion of the flow boundary configuration; and

first attractor electrode means disposed at an opposite side of the flow path so as to be substantially flush with the immediately downstream portion of the flow boundary configuration in opposed relation to the discharge electrode means, the discharge and attractor electrode means extending laterally of the flow path in the direction of boundary configuration elongation and having at least portions thereof electrically exposed to the flow path to form a fluid ionizing electrode pair;

the discharge and attractor electrode means and the boundary establishing means forming a substantially smooth, continuous flow path to reduce friction losses upon movement of the fluid through the apparatus 2. Apparatus as set forth in claim 1, further comprising:

at least one additional discharge electrode means and at least one additional attractor electrode means disposed, respectively, to be substantially flush with the flow boundary configuration, the additional discharge and attractor electrode means being in opposed relation and spaced at a distance downstream from the first discharge and attractor electrode means to form an additional ionizing electrode pair;

each of the additional electrodes and the boundary establishing means establishing a substantially smooth continuous transition therebetween to reduce friction losses resulting from the presence of the additional electrodes.

3. Apparatus in accordance with claim 2, further comprising:

collector electrode means downstream of the attractor and discharge electrode means and disposed in relation to the flow path to collect ions from the fluid stream; and

a voltage divider network in the form of a resistive film superposed on a surface of the guide means, the network being electrically connected between the collector electrode means and at least one electrode pair to develop an ionizing potential therebetween.

4. Apparatus as set forth in claim 2, wherein consecutive discharge electrodes and consecutive attractor electrodes are located at opposite sides of the flow path from preceding discharge electrodes and attractor electrodes, respectively.

5. Apparatus as defined in claim 4 in which each associated pair of discharge and attractor electrodes and a distance of the flow path therefrom to a consecutive electrode form an electrogasdynamic converter stage, the apparatus further comprising:

source means connected to alternate electrode pairs for ionizing the fluid to produce ions of opposite electrical polarity in consecutive stages;

means for connecting one side of an external circuit to the discharge electrode means at one side of the flow path; and

means for connecting the other side of the external circuit to the discharge electrodes at the other side of the flow path.

6. Apparatus as defined in claim 1, in which:

said boundary configuration establishing means comprises means increasing the cross section of the boundary configuration progressively in the area between the inlet and the outlet ofthe fluid guide means to prevent constriction of the stream by electrically produced forces thereon.

7. Apparatus in accordance with claim 6 wherein:

the transverse dimension of the boundary configuration is substantially constant.

8. Apparatus in accordance with claim 7 wherein:

the constant dimension is greater than approximately 1 millimeter and less than approximately millimeters.

9. Apparatus as defined in claim I wherein the discharge electrode means comprises a thin wire; and the thin wire is partially embedded in the fluid guide means to leave only a portion ofthe surface exposed to the flow path.

10. Apparatus in accordance with claim 1 wherein the discharge electrode means comprises:

a narrow, thin-film conductive strip superposed on an inside surface of the guide means and presenting to the flow path a line of corona discharge when an ionizing potential, relative to the attractor electrode means, is applied thereto.

11. Apparatus in accordance with claim 1 wherein the discharge means comprises:

a thin strip of conductive material disposed transversely in the guide means to leave exposed to the flow path an edge substantially flush with the flow boundary configuration and forming a line of corona discharge when a ionizing potential, relative to the attractor electrode, is applied thereto.

12. Apparatus according to claim l,further comprising:

plural electroconductive electrical field shielding means for substantially reducing the effect of electrical fields adjacent the flow path boundary;

the shielding means extending laterally of the flow path and including electroconductive elements mutually spaced along the axis of flow downstream of the electrode means; and

means for establishing a conductive path interconnecting the electroconductive elements.

13. Apparatus according to claim 12 in which:

the electroconductive shielding means comprises conductive elements disposed to be surrounded by the stream, each element being spaced sufficiently closely to an adjacent such element to establish a thin boundary layer of fluid when said stream is passed therethrough at subsonic flow conditions, thereby establishing a part of said flow boundary.

14. Apparatus for ionizing a stream of fluid comprising:

fluid guide means having an inlet and outlet and defining therebetween a flow path for the fluid, the interior of the guide means having a dielectric surface providing a flow boundary configuration;

corona discharge electrode means extending laterally of and disposed at a side of the flow path, the corona discharge electrode means comprising a narrow thin-film strip of conductive ceramic material superposed on the dielectric surface of the guide means; and

attractor electrode means disposed at an opposite side of the flow path in opposed relation to the corona discharge electrode means and comprising a thin-film strip of conductive ceramic material superposed on the dielectric surface, the attractor electrode means being substantially wider than the corona electrode means in the direction of fluid flow.

15. Apparatus in accordance with claim 17 wherein:

the ceramic material is selected from the group consisting of zirconium diboride, titanium diboride, zirconium carbide, boron carbide, titanium carbide, and vanadium carbide.

16. In electrogasdynamic arrangements for effecting an electrogasdynamic energy exchange, apparatus for ionizing a stream of fluid including the combination of:

fluid guide means providing a plurality of parallel flow paths for the fluid each having an inlet and an outlet, the fluid guide means including flow separating means defining flow path bounds along which at least portions thereof are nonconducting so as to avoid a continuous conductive surface adjacent the flow paths for establishing plural flow paths of elongate cross section in fluid flow areas free of discharge, attractor, and collector electrodes;

electrical discharge electrode means at an upstream end of each flow path having a charge emitting surface exposed to the flow path to release an electrical discharge of one polarity thereinto; and

attractor electrode means at the upstream end of each flow path disposed to have a surface thereof exposed to the flow path, each attractor electrode means forming with a respective discharge electrode means an ionizing electrode pair to create therebetween an electrical discharge field for ionizing the fluid.

17. Apparatus as defined in claim 16 in which:

the flow separating means includes a plurality of spaced, generally parallel dielectric plates, with the spaces between adjacent ones thereof forming fluid flow channels.

18. Apparatus as defined in claim 16, in which:

the flow separating means includes a plurality ofelectroconductive elements exposed to the flow and mutually spaced in the direction of flow.

19. Apparatus according to claim 18, further comprising:

means for interconnecting the electroconductive elements through a circuit to establish potential differences between at least two of such elements.

20. Apparatus according to claim 18, in which:

the electroconductive elements extend laterally of the flow in a plurality of transversely spaced rows.

21. Apparatus according to claim 20, in which:

the electroconductive elements of adjacent rows are axially spaced.

22. Apparatus according to claim 21, further comprising:

circuit means interconnecting the electroconductive elements of adjacent rows to establish on axially consecutive ones thereof progressively different electrical potentials effective to limit the electrical space charge field in the flow paths.

23. Apparatus as defined in claim 16, further comprising:

a collecting chamber disposed to receive ionized fluid flow from the outlets of the flow paths and defining a further boundary configuration for the stream, the further boundary configuration having a cross-sectional area normal to the flow which is greater than the combined corresponding cross-sectional areas of the flow paths.

24. Apparatus as set forth in claim 23, in which:

the collecting chamber has a conductive surface at the boundary of the flow and exposed to the fluid from the flow channel outlets.

25. Apparatus as defined in claim 23, wherein:

the axial dimension of the flow separating means between the ionizing electrode pairs and the outlets of the flow channels is at least as great as one-half the shortest dimension of the collecting chamber normal to the axis of fluid flow.

26. Apparatus as defined in claim 23, in which the collecting chamber is a conduit in which the ionized flow produces a space charge field, the apparatus further comprising:

passive conductor means associated with and electrically isolated from the conduit and operable in the space charge field for enhancing the space charge field electrical gradient normal to the conduit axis at downstream locations in the conduit.

27. Apparatus in accordance with claim 16, in which:

the attractor electrode means comprises a pair of conductive plates extending axially of the flow path from the upstream end of the fluid guide means to form the inlet to the fluid guide means, and

the electrical discharge electrode means comprises a thin wirelike element disposed between the attractor electrode plates.

28. Apparatus as defined in claim 16, in which:

at least one of the electrical discharge and attractor electrode means forms an axial extension of the fluid guide means in the upstream direction ofthe flow path, and

the cross-sectional area normal to the flow path of the boundary configuration defined by the extension is greater than the cross-sectional area of the boundary configuration defined by the bounds defining means downstream thereof.

29. Apparatus according to claim 16, in which:

both the attractor and discharge electrode means have a surface thereof substantially flush with the flow path boundary and extending in the direction of flow path boundary elongation, the discharge and attractor electrodes being disposed at opposite sides of the flow path.

30. Apparatus according to claim 16, further comprising second attractor electrode means having a conductive surface exposed to the flow path and being effective on the electrical discharge to extend the dimension of the discharge field in the direction of the axis of fluid flow.

31. Apparatus according to claim 30, in which:

the first attractor electrode means includes conductive surfaces exposed to the flow path at respective opposite sides thereof, and

the second attractor electrode means also includes at least one conductive surface located in the flow path intermediate the respective opposite sides ofthe flow path axially spaced from the first attractor electrode.

32. Apparatus according to claim 16, further comprising: '5 collector electrode means downstream of the electrical discharge and attractor electrode means; and means for connecting the collector electrode means to an electrical load to receive from the collector electrode electrical charges carried by the flow.

2 33. Electrogasdynamic apparatus for ionizing a stream of fluid comprising:

fluid guide means having an inlet and an outlet and providing therebetween a channel in the stream; means in the guide means defining a plurality of parallel 25 flow paths for the stream, the flow paths having a substantially rectangular boundary configuration of which the cross-sectional area progressively increases from the inlet to the outlet of the guide means;

corona discharge electrode means extending laterally of and disposed at a side of each of the flow paths; and

attractor electrode means disposed at an opposite side of each of the flow paths in opposed relation to the respective corona discharge electrode means, the corona discharge and attractor electrode means having at least portions thereof electrically exposed to the flow path, the corona discharge and attractor electrode means of each flow path being electrically connected, respectively, to the corresponding corona discharge and attractor electrode means of the other flow paths;

the increase in cross-sectional area of the flow paths following associated corona and attractor electrode means being effective to reduce the tendency toward ion acceleration following charging ofthe stream.

34. Apparatus in accordance with claim 33, in which the means defining the plurality of flow paths is a plurality of generally parallel dielectric plates.

35. Apparatus as set forth in claim 33 in which the means defining the plurality of flow paths comprises:

a plurality of layers of elongated wirelike electroconductive elements extending laterally of the flow paths to provide said boundary configuration.

36. Apparatus in accordance with claim 35, in which the electroconductive elements are dielectrically coated.

37. Apparatus in accordance with claim 33 wherein:

each of the flow paths has approximately the same transverse dimension. 38. Apparatus in accordance with claim 33, further comprising:

collector electrode means downstream of the attractor and corona discharge electrode means and disposed laterally and at the side of each of the respective flow paths, the collector electrode means having an electrical characteristic to neutralize ions in the fluid stream.

39. Electrogasdynamic apparatus operative on a stream of fluid to effect a conversion between the energy of the fluid and electrical energy, comprising:

fluid guide means having an inlet and an outlet and providing therebetween a channel for the stream;

a plurality of spaced-apart, substantially parallel dielectric plates in the guide means defining a plurality of parallel flow paths for the fluid;

the flow paths having a substantially rectangular boundary configuration of which the cross-sectional area progressively increases from the inlet and to the outlet;

KII

a plurality of elongate corona discharge electrodes disposed laterally of and at a side of each of the flow paths, the corona discharge electrodes being spaced apart in the direction of fluid flow; and

a plurality ofelongate attractor electrodes disposed laterally of and at an opposite side of the respective flow paths in opposed relation to and paired with the respective corona discharge electrodes, the several corona discharge and attractor electrodes providing conductive portions substantially flush with the respective surfaces of the dielectric plates so as to be electrically exposed to the flow paths.

40. Apparatus for ionizing a stream of fluid, comprising:

fluid guide means having an inlet and means for establishing therebetween a flow path boundary configuration for the fluid stream;

electrical discharge electrode means downstream of the fluid guide means inlet and having a charge-emitting surface exposed to the flow path to release an electrical discharge, thereinto;

first attractor electrode means disposed to have at least one surface thereof exposed to the flow path to form with the discharge electrode means a first ionizing electrode pair for creating an electrical space charge field downstream thereof; and

second attractor electrode means associated with the discharge electrode means and having at least one conductive surface disposed in the path of flow, the second attractor electrode means being effective on the electrical discharge to extend the dimension of the ionizing field in the direction offluid flow.

4]. Apparatus as set forth in claim 40, in which:

the conductive surface of the second attractor electrode means is located downstream of the first attractor electrode means.

42. Apparatus as defined in claim 40, in which:

the upstream attractor electrode means includes a pair of conductive surfaces located at respective opposite sides of the flow path, and

the conductive surface of the second attractor electrode means is disposed intermediate the respective opposite sides of the flow path.

43. Apparatus as defined in claim 40, further comprising:

dielectric divider means for supporting the second attractor electrode means and dividing the flow in the guide means into two separate parallel fluid streams, the second attractor electrode means including a surface exposed to each of the parallel fluid streams.

44. Apparatus as defined in claim 40 further comprising:

means for applying an electrical potential, relative to the electrical discharge means, to the first attractor electrode means sufficient to effect ionization of the fluid stream, and

means for applying an electrical potential of the same polarity to the second attractor electrode means of greater magnitude than the potential applied to the first attractor electrode means to attract ions in the flow path axially thereto.

45. ln electrogasdynamic apparatus for ionizing a stream of fluid guide means having an inlet and an outlet and including a pair of spaced dielectric members defining therebetween an elongate flow boundary configuration;

attractor electrode means including a conductive surface extending in the upstream direction from the upstream ends of the dielectric members to form therebetween the inlet for the fluid guide means, the inlet being of an enlarged cross-sectional area normal to the flow path and converging to a smaller cross-sectional area of the flow path immediately adjacent thereto; and

electrical discharge electrode means associated with the attractor electrode means and forming therewith an ionizing electrode pair for subjecting the fluid stream at the inlet to an electrical discharge field.

46. Apparatus according to claim 45, in which:

the discharge electrode means comprises a plurality of spaced apart thin, wirelike elements, arranged in a plane substantially parallel to the fluid stream and intermediate the conductive surfaces ofthe attractor electrode means.

47. Electrogasdynamic apparatus for operating on a stream offluid, comprising: I

means defining a flow path for the fluid having an inlet and an outlet;

means for ionizing the fluid in an upstream portion of the flow path to create a space charge field downstream thereof;

a conduit disposed to receive the ionized fluid from the outlet of the flow path defining means and thereby to have a space charge field in the interior thereof for collecting the electrical charges carried by the fluid, fluid guide means for defining a substantially nonconducting boundary portion intermediate the ionizing and collecting means; and

passive conductor means associated with and electrically isolated from the conduit and operable in the space charge field for enhancing the space charge field electrical gradient normal to the conduit axis at downstream locations in the conduit.

48. Apparatus in accordance with claim 47, in which:

the conductor is elongated in the direction of fluid flow and has a substantial downstream portion electrically insulated from the flow, with at least an upstream portion exposed to the flow to be energized by the charges carried by the fluid.

49. Apparatus as defined in claim 48, wherein: the conductor is coaxial with the conduit.

50. Apparatus as defined in claim 47, further comprising:

means for applying to the passive conductor means an electrical potential to establish between the passive conductor and points surrounding it an electrical field transverse of the direction of flow.

51. An electrogasdynamic apparatus for operating on a stream of gas comprising:

an enclosure having an inlet and an outlet for the stream;

electrical discharge electrode means at an upstream location in the enclosure for injecting electrical charges into the stream; and

a plurality of electroconductive elements extending interiorly of the enclosure, transversely of and in the flow of downstream of the electrical discharge means, and being mutually spaced in the direction of flow;

the enclosure being free of other charging, attracting, and charge collecting electrodes in the enclosure portion housing the conductive elements; and

means for connecting the electroconductive elements to an electrical circuit to establish on each thereof a reference potential to modify the electric field within the enclosure.

52. Apparatus according to claim 51, in which:

the electroconductive elements are disposed in at least one plane parallel to the direction of flow between the inlet and outlet of the enclosure and intermediate sides of the enclosure.

53. Apparatus according to claim 51, in which:

the electroconductive elements are disposed in at least two spaced planes parallel to the direction of flow between the inlet and outlet of the enclosure.

54. Apparatus according to claim 51, in which:

the electroconductive elements comprise a plurality of conductors having a maximum cross-sectional dimension substantially less than the smallest cross-sectional dimension of any flow path for the stream within the enclosure.

55. Apparatus according to claim 51, in which:

the reference potential on electroconductive elements at a given axial location differs from the reference potential on electroconductive elements at a different axial location.

56. Apparatus according to claim 51, further comprising:

collector electrode means exposed to the stream downstream of the electroconductive elements and means for connecting the collector electrode to an external electrical circuit.

57. Apparatus according to claim in which:

the electrical circuit comprises a resistive film on the enclosure, and

the axially displaced ele-z'troconductive elements are electrically connected to points along the resistive film to connect an impedance between the axially displaced elements.

58. An electrogasdynamic apparatus for operating on a stream of gas, comprising:

means defining an enclosure having an inlet and outlet for the stream;

electrical discharge means at an upstream location in the enclosure for injecting electrical charges into the stream; and

an array of electroconductive shielding elements disposed in the stream at a downstream location for establishing a reference potential at each thereof effective to limit the maximum space charge field between the electrical discharge means and the outlet by shielding sections of the enclosure from electrical charge concentrations in the stream at other sections of the enclosure.

59. In apparatus for ionizing a gaseous stream:

guide means including a pair of parallel, spaced-apart dielectric plates defining therebetween a flow channel for the stream of gas and having an inlet and an outlet; and

ionizing electrode means at an upstream location in the guide means for creating an electrical discharge field in the flow channel, the discharge field being effective to produce mobile charge carriers to be forced downstream by the stream;

the dielectric plates having passages therein unexposed to the stream for directing a coolant therethrough to effect a transfer of heat from the stream and to the plates downstream of the electrical discharge field.

60. In an electrogasdynamic device, defining an axial flow path for a stream of gas carrying electrical charges, the improvement comprising:

an outer, axially elongate channel member for passage of the gas therethrough,

means for establishing the electrical charges carried by the gas through the channel,

means for controlling the electric field distribution across the interior of the channel member downstream from the charge establishing means,

the field controlling means including an array of axially spaced electroconductive shielding elements within the channel member and disposed in the stream to extend thereacross removed from the means for establishing the electrical charges, and

means, connected with the shielding elements, for establishing on axially spaced elements a different electrical potential to control the axial electric field gradient within the channel member. 61. The improvement according to claim 60, in which: at least some of the elements are mutually spaced transversely of the flow path.

62. The improvement according to claim 60, in which:

the electroconductive elements present conductive surfaces to the gas stream and are electrically connected to drain off charges, thereby reducing excessive electrical charge buildup within the channel.

63. The improvement of claim 62, in which: the elements comprise metal rodlike members.

Claims (63)

1. Electrogasdynamic converter apparatus for ionizing a stream of fluid comprising: fluid guide means having a inlet and outlet and means for establishing therebetween a flow path boundary configuration for the stream when the stream is passed therethrough, the boundary configuration having a substantially elongate cross section; first electrical discharge electrode means disposed at a side of the flow path so as to be substantially flush with the immediately downstream portion of the flow boundary configuration; and first attractor electrode means disposed at an opposite side of the flow path so as to be substantially flush with the immediately downstream portion of the flow boundary configuration in opposed relation to the discharge electrode means, the discharge and attractor electrode means extending laterally of the flow path in the direction of boundary configuration elongation and having at least portions thereof electrically exposed to the flow path to form a fluid ionizing electrode pair; the discharge and attractor electrode means and the boundary establishing means forming a substantially smooth, continuous flow path to reduce friction losses upon movement of the fluid through the apparatus

2. Apparatus as set forth in claim 1, further comprising: at least one additional discharge electrode means and at least one additional attractor electrode means disposed, respectively, to be substantially flush with the flow boundary configuration, the additional discharge and attractor electrode means being in opposed relation and spaced at a distance downstream from the first discharge and attractor electrode means to form an additional ionizing electrode pair; each of the additional electrodes and the boundary establishing means establishing a substantially smooth continuous transition therebetween to reduce friction losses resulting from the presence of the additional electrodes.

3. Apparatus in accordance with claim 2, further comprising: collector electrode means downstream of the attractor and discharge electrode means and disposed in relation to the flow path to collect ions from the fluid stream; and a voltage divider network in the form of a resistive film superposed on a surface of the guide means, the network being electrically connected between the collector electrode means and at least one electrode pair to develop an ionizing potential therebetween.

4. Apparatus as set forth in claim 2, wherein consecutive discharge electrodes and consecutive attractor electrodes are located at opposite sides of the flow path from preceding discharge electrodes and attractor electrodes, respectively.

5. Apparatus as defined in claim 4 in which each associated pair of discharge and attractor electrodes and a distance of the flow path therefrom to a consecutive electrode form an electrogasdynamic converter stage, the apparatus further comprising: source means connected to alternate electrode pairs for ionizing the fluid to produce ions of opposite electrical polarity in consecutive stages; means for connecting one side of an external circuit to the discharge electrode means at one side of the flow path; and means for connecting the other side of the external circuit to the discharge electrodes at the other side of the flow path.

6. Apparatus as defined in claim 1, in which: said boundary configuration establishing means comprises means increasing the cross section of the boundary configuration progressively in the area between the inlet and the outlet of the fluid guide means to prevent constriction of the stream by electrically produced forces thereon.

7. Apparatus in accordance with claim 6 wherein: the transverse dimension of the boundary configuration is substantially constant.

8. Apparatus in accordance with claim 7 wherein: the constant dimension is greater than approximately 1 millimeter and less than approximately 5 millimeters.

9. Apparatus as defined in claim 1 wherein the discharge electrode means comprises a thin wire; and the thin wire is partially embedded in the fluid guide means to leave only a portion of the surface exposed to the flow path.

10. Apparatus in accordance with claim 1 wherein the discharge electrode means comprises: a narrow, thin-film conductive strip superposed on an inside surface of the guide means and presenting to the flow path a line of corona discharge when an ionizing potential, relative to the attractor electrode means, is applied thereto.

11. Apparatus in accordance with claim 1 wherein the discharge means comprises: a thin strip of conductive material disposed transversely in the guide means to leave exposed to the flow path an edge substantially flush with the flow boundary configuration and forming a line of corona discharge when a ionizing potential, relative to the attractor electrode, is applied thereto.

12. Apparatus according to claim 1, further comprising: plural electroconductive electrical field shielding means for substantially reducing the effect of electrical fields adjacent the flow path boundary; the shielding means extending laterally of the flow path and including electroconductive elements mutually spaced along the axis of flow downstream of the electrode means; and means for establishing a conductive path interconnecting the electroconductive elements.

13. Apparatus according to claim 12 in which: the electroconductive shielding means comprises conductive elements disposed to be surrounded by the stream, each element being spaced sufficiently closely to an adjacent such element to establish a thin boundary layer of fluid when said stream is passed therethrough at subsonic flow conditions, thereby establishing a part of said flow boundary.

14. Apparatus for ionizing a stream of fluid comprising: fluid guide means having an inlet and outlet and defining therebetween a flow path for the fluid, the interior of the guide means having a dielectric surface providing a flow boundary configuration; corona discharge electrode means extending lateRally of and disposed at a side of the flow path, the corona discharge electrode means comprising a narrow thin-film strip of conductive ceramic material superposed on the dielectric surface of the guide means; and attractor electrode means disposed at an opposite side of the flow path in opposed relation to the corona discharge electrode means and comprising a thin-film strip of conductive ceramic material superposed on the dielectric surface, the attractor electrode means being substantially wider than the corona electrode means in the direction of fluid flow.

15. Apparatus in accordance with claim 17 wherein: the ceramic material is selected from the group consisting of zirconium diboride, titanium diboride, zirconium carbide, boron carbide, titanium carbide, and vanadium carbide.

16. In electrogasdynamic arrangements for effecting an electrogasdynamic energy exchange, apparatus for ionizing a stream of fluid including the combination of: fluid guide means providing a plurality of parallel flow paths for the fluid each having an inlet and an outlet, the fluid guide means including flow separating means defining flow path bounds along which at least portions thereof are nonconducting so as to avoid a continuous conductive surface adjacent the flow paths for establishing plural flow paths of elongate cross section in fluid flow areas free of discharge, attractor, and collector electrodes; electrical discharge electrode means at an upstream end of each flow path having a charge emitting surface exposed to the flow path to release an electrical discharge of one polarity thereinto; and attractor electrode means at the upstream end of each flow path disposed to have a surface thereof exposed to the flow path, each attractor electrode means forming with a respective discharge electrode means an ionizing electrode pair to create therebetween an electrical discharge field for ionizing the fluid.

17. Apparatus as defined in claim 16 in which: the flow separating means includes a plurality of spaced, generally parallel dielectric plates, with the spaces between adjacent ones thereof forming fluid flow channels.

18. Apparatus as defined in claim 16, in which: the flow separating means includes a plurality of electroconductive elements exposed to the flow and mutually spaced in the direction of flow.

19. Apparatus according to claim 18, further comprising: means for interconnecting the electroconductive elements through a circuit to establish potential differences between at least two of such elements.

20. Apparatus according to claim 18, in which: the electroconductive elements extend laterally of the flow in a plurality of transversely spaced rows.

21. Apparatus according to claim 20, in which: the electroconductive elements of adjacent rows are axially spaced.

22. Apparatus according to claim 21, further comprising: circuit means interconnecting the electroconductive elements of adjacent rows to establish on axially consecutive ones thereof progressively different electrical potentials effective to limit the electrical space charge field in the flow paths.

23. Apparatus as defined in claim 16, further comprising: a collecting chamber disposed to receive ionized fluid flow from the outlets of the flow paths and defining a further boundary configuration for the stream, the further boundary configuration having a cross-sectional area normal to the flow which is greater than the combined corresponding cross-sectional areas of the flow paths.

24. Apparatus as set forth in claim 23, in which: the collecting chamber has a conductive surface at the boundary of the flow and exposed to the fluid from the flow channel outlets.

25. Apparatus as defined in claim 23, wherein: the axial dimension of the flow separating means between the ionizing electrode pairs and the outlets of the flow channels is at least as great as one-half the shortest dimension of the collecting chamber normal to the axiS of fluid flow.

26. Apparatus as defined in claim 23, in which the collecting chamber is a conduit in which the ionized flow produces a space charge field, the apparatus further comprising: passive conductor means associated with and electrically isolated from the conduit and operable in the space charge field for enhancing the space charge field electrical gradient normal to the conduit axis at downstream locations in the conduit.

27. Apparatus in accordance with claim 16, in which: the attractor electrode means comprises a pair of conductive plates extending axially of the flow path from the upstream end of the fluid guide means to form the inlet to the fluid guide means, and the electrical discharge electrode means comprises a thin wirelike element disposed between the attractor electrode plates.

28. Apparatus as defined in claim 16, in which: at least one of the electrical discharge and attractor electrode means forms an axial extension of the fluid guide means in the upstream direction of the flow path, and the cross-sectional area normal to the flow path of the boundary configuration defined by the extension is greater than the cross-sectional area of the boundary configuration defined by the bounds defining means downstream thereof.

29. Apparatus according to claim 16, in which: both the attractor and discharge electrode means have a surface thereof substantially flush with the flow path boundary and extending in the direction of flow path boundary elongation, the discharge and attractor electrodes being disposed at opposite sides of the flow path.

30. Apparatus according to claim 16, further comprising: second attractor electrode means having a conductive surface exposed to the flow path and being effective on the electrical discharge to extend the dimension of the discharge field in the direction of the axis of fluid flow.

31. Apparatus according to claim 30, in which: the first attractor electrode means includes conductive surfaces exposed to the flow path at respective opposite sides thereof, and the second attractor electrode means also includes at least one conductive surface located in the flow path intermediate the respective opposite sides of the flow path axially spaced from the first attractor electrode.

32. Apparatus according to claim 16, further comprising: collector electrode means downstream of the electrical discharge and attractor electrode means; and means for connecting the collector electrode means to an electrical load to receive from the collector electrode electrical charges carried by the flow.

33. Electrogasdynamic apparatus for ionizing a stream of fluid comprising: fluid guide means having an inlet and an outlet and providing therebetween a channel in the stream; means in the guide means defining a plurality of parallel flow paths for the stream, the flow paths having a substantially rectangular boundary configuration of which the cross-sectional area progressively increases from the inlet to the outlet of the guide means; corona discharge electrode means extending laterally of and disposed at a side of each of the flow paths; and attractor electrode means disposed at an opposite side of each of the flow paths in opposed relation to the respective corona discharge electrode means, the corona discharge and attractor electrode means having at least portions thereof electrically exposed to the flow path, the corona discharge and attractor electrode means of each flow path being electrically connected, respectively, to the corresponding corona discharge and attractor electrode means of the other flow paths; the increase in cross-sectional area of the flow paths following associated corona and attractor electrode means being effective to reduce the tendency toward ion acceleration following charging of the stream.

34. Apparatus in accordance with claim 33, in which the means defining the plurality of flow paths is a plurality of genErally parallel dielectric plates.

35. Apparatus as set forth in claim 33 in which the means defining the plurality of flow paths comprises: a plurality of layers of elongated wirelike electroconductive elements extending laterally of the flow paths to provide said boundary configuration.

36. Apparatus in accordance with claim 35, in which the electroconductive elements are dielectrically coated.

37. Apparatus in accordance with claim 33 wherein: each of the flow paths has approximately the same transverse dimension.

38. Apparatus in accordance with claim 33, further comprising: collector electrode means downstream of the attractor and corona discharge electrode means and disposed laterally and at the side of each of the respective flow paths, the collector electrode means having an electrical characteristic to neutralize ions in the fluid stream.

39. Electrogasdynamic apparatus operative on a stream of fluid to effect a conversion between the energy of the fluid and electrical energy, comprising: fluid guide means having an inlet and an outlet and providing therebetween a channel for the stream; a plurality of spaced-apart, substantially parallel dielectric plates in the guide means defining a plurality of parallel flow paths for the fluid; the flow paths having a substantially rectangular boundary configuration of which the cross-sectional area progressively increases from the inlet and to the outlet; a plurality of elongate corona discharge electrodes disposed laterally of and at a side of each of the flow paths, the corona discharge electrodes being spaced apart in the direction of fluid flow; and a plurality of elongate attractor electrodes disposed laterally of and at an opposite side of the respective flow paths in opposed relation to and paired with the respective corona discharge electrodes, the several corona discharge and attractor electrodes providing conductive portions substantially flush with the respective surfaces of the dielectric plates so as to be electrically exposed to the flow paths.

40. Apparatus for ionizing a stream of fluid, comprising: fluid guide means having an inlet and means for establishing therebetween a flow path boundary configuration for the fluid stream; electrical discharge electrode means downstream of the fluid guide means inlet and having a charge-emitting surface exposed to the flow path to release an electrical discharge, thereinto; first attractor electrode means disposed to have at least one surface thereof exposed to the flow path to form with the discharge electrode means a first ionizing electrode pair for creating an electrical space charge field downstream thereof; and second attractor electrode means associated with the discharge electrode means and having at least one conductive surface disposed in the path of flow, the second attractor electrode means being effective on the electrical discharge to extend the dimension of the ionizing field in the direction of fluid flow.

41. Apparatus as set forth in claim 40, in which: the conductive surface of the second attractor electrode means is located downstream of the first attractor electrode means.

42. Apparatus as defined in claim 40, in which: the upstream attractor electrode means includes a pair of conductive surfaces located at respective opposite sides of the flow path, and the conductive surface of the second attractor electrode means is disposed intermediate the respective opposite sides of the flow path.

43. Apparatus as defined in claim 40, further comprising: dielectric divider means for supporting the second attractor electrode means and dividing the flow in the guide means into two separate parallel fluid streams, the second attractor electrode means including a surface exposed to each of the parallel fluid streams.

44. Apparatus as defined in claim 40 further comprising: means for applying an electrical potential, relative to the electrical discharge Means, to the first attractor electrode means sufficient to effect ionization of the fluid stream, and means for applying an electrical potential of the same polarity to the second attractor electrode means of greater magnitude than the potential applied to the first attractor electrode means to attract ions in the flow path axially thereto.

45. In electrogasdynamic apparatus for ionizing a stream of fluid: fluid guide means having an inlet and an outlet and including a pair of spaced dielectric members defining therebetween an elongate flow boundary configuration; attractor electrode means including a conductive surface extending in the upstream direction from the upstream ends of the dielectric members to form therebetween the inlet for the fluid guide means, the inlet being of an enlarged cross-sectional area normal to the flow path and converging to a smaller cross-sectional area of the flow path immediately adjacent thereto; and electrical discharge electrode means associated with the attractor electrode means and forming therewith an ionizing electrode pair for subjecting the fluid stream at the inlet to an electrical discharge field.

46. Apparatus according to claim 45, in which: the discharge electrode means comprises a plurality of spaced apart thin, wirelike elements, arranged in a plane substantially parallel to the fluid stream and intermediate the conductive surfaces of the attractor electrode means.

47. Electrogasdynamic apparatus for operating on a stream of fluid, comprising: means defining a flow path for the fluid having an inlet and an outlet; means for ionizing the fluid in an upstream portion of the flow path to create a space charge field downstream thereof; a conduit disposed to receive the ionized fluid from the outlet of the flow path defining means and thereby to have a space charge field in the interior thereof for collecting the electrical charges carried by the fluid, fluid guide means for defining a substantially nonconducting boundary portion intermediate the ionizing and collecting means; and passive conductor means associated with and electrically isolated from the conduit and operable in the space charge field for enhancing the space charge field electrical gradient normal to the conduit axis at downstream locations in the conduit.

48. Apparatus in accordance with claim 47, in which: the conductor is elongated in the direction of fluid flow and has a substantial downstream portion electrically insulated from the flow, with at least an upstream portion exposed to the flow to be energized by the charges carried by the fluid.

49. Apparatus as defined in claim 48, wherein: the conductor is coaxial with the conduit.

50. Apparatus as defined in claim 47, further comprising: means for applying to the passive conductor means an electrical potential to establish between the passive conductor and points surrounding it an electrical field transverse of the direction of flow.

51. An electrogasdynamic apparatus for operating on a stream of gas comprising: an enclosure having an inlet and an outlet for the stream; electrical discharge electrode means at an upstream location in the enclosure for injecting electrical charges into the stream; and a plurality of electroconductive elements extending interiorly of the enclosure, transversely of and in the flow of downstream of the electrical discharge means, and being mutually spaced in the direction of flow; the enclosure being free of other charging, attracting, and charge collecting electrodes in the enclosure portion housing the conductive elements; and means for connecting the electroconductive elements to an electrical circuit to establish on each thereof a reference potential to modify the electric field within the enclosure.

52. Apparatus according to claim 51, in which: the electroconductive elements are disposed in at least one plane parallel to the direction of flow between the inlet and outleT of the enclosure and intermediate sides of the enclosure.

53. Apparatus according to claim 51, in which: the electroconductive elements are disposed in at least two spaced planes parallel to the direction of flow between the inlet and outlet of the enclosure.

54. Apparatus according to claim 51, in which: the electroconductive elements comprise a plurality of conductors having a maximum cross-sectional dimension substantially less than the smallest cross-sectional dimension of any flow path for the stream within the enclosure.

55. Apparatus according to claim 51, in which: the reference potential on electroconductive elements at a given axial location differs from the reference potential on electroconductive elements at a different axial location.

56. Apparatus according to claim 51, further comprising: collector electrode means exposed to the stream downstream of the electroconductive elements and means for connecting the collector electrode to an external electrical circuit.

57. Apparatus according to claim 51, in which: the electrical circuit comprises a resistive film on the enclosure, and the axially displaced electroconductive elements are electrically connected to points along the resistive film to connect an impedance between the axially displaced elements.

58. An electrogasdynamic apparatus for operating on a stream of gas, comprising: means defining an enclosure having an inlet and outlet for the stream; electrical discharge means at an upstream location in the enclosure for injecting electrical charges into the stream; and an array of electroconductive shielding elements disposed in the stream at a downstream location for establishing a reference potential at each thereof effective to limit the maximum space charge field between the electrical discharge means and the outlet by shielding sections of the enclosure from electrical charge concentrations in the stream at other sections of the enclosure.

59. In apparatus for ionizing a gaseous stream: guide means including a pair of parallel, spaced-apart dielectric plates defining therebetween a flow channel for the stream of gas and having an inlet and an outlet; and ionizing electrode means at an upstream location in the guide means for creating an electrical discharge field in the flow channel, the discharge field being effective to produce mobile charge carriers to be forced downstream by the stream; the dielectric plates having passages therein unexposed to the stream for directing a coolant therethrough to effect a transfer of heat from the stream and to the plates downstream of the electrical discharge field.

60. In an electrogasdynamic device, defining an axial flow path for a stream of gas carrying electrical charges, the improvement comprising: an outer, axially elongate channel member for passage of the gas therethrough, means for establishing the electrical charges carried by the gas through the channel, means for controlling the electric field distribution across the interior of the channel member downstream from the charge establishing means, the field controlling means including an array of axially spaced electroconductive shielding elements within the channel member and disposed in the stream to extend thereacross removed from the means for establishing the electrical charges, and means, connected with the shielding elements, for establishing on axially spaced elements a different electrical potential to control the axial electric field gradient within the channel member.

61. The improvement according to claim 60, in which: at least some of the elements are mutually spaced transversely of the flow path.

62. The improvement according to claim 60, in which: the electroconductive elements present conductive surfaces to the gas stream and are electrically connected to drain off charges, thereby reducing excessive electrical charge buildup within the channel.

63. The improvEment of claim 62, in which: the elements comprise metal rodlike members.

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